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Effective control of magnetic anisotropy, including perpendicular magnetic anisotropy (PMA) and lateral magnetic anisotropy, is important for the design of low-power and high-density spintronic devices. However, the rarity of oxide materials with PMA and stringent conditions required to control magnetic anisotropy have prevented its large-scale application. Here, we demonstrate that the magnetic anisotropy of SrRuO3 films can be specified on-demand by adjusting the content of Ru vacancies to control the structure of the films. With the increase in Ru vacancies, the structure of SrRuO3 changes from orthorhombic to tetragonal. The field angle dependence of the Hall resistance confirmed that the uniaxial magnetic easy axis of SrRuO3 thin films continuously rotates in the (100)pc crystallographic plane, which is identical to the continuous phase transition. Our results not only provide a way to continuously tune the physical properties of epitaxial oxide films by continuously changing the composition but also help to provide guidance for the on-demand design of spintronic devices.

The interplay of internal charge and spin degrees of freedom in diluted magnetic semiconductors (DMSs) determines the magnetic, electrical, and optical properties for desired spintronic devices. However, elusive signs in DMSs, such as Curie temperatures far over 300 K, long-range magnetic order at concentrations of magnetic cations of a few percent, temperature-insensitive, and anhysteretic ferromagnetism, challenge our understanding of magnetism in solids. To approach the truth, the magnetism of Mo-doped BaSnO3 was investigated in this work from experiments to density functional theory (DFT) calculations. Electron spin resonance measurements confirm the existence of oxygen vacancies in the samples, and BaMo0.0625Sn0.9375O3−δ, where δ represents the number of oxygen vacancies, displays much weaker ferromagnetism compared to the DFT results without spin–orbit coupling (SOC). Therefore, a small orbital contribution restored in spin–orbit coupling (SOC) was introduced for the partial density of states and band structure calculations. The modified DFT calculations indicate that the increase in oxygen vacancies leads to an obvious reduction of the total density of states (DOS) near Fermi level (EF), lower dispersity of the conduction band, and deep localized states in the bandgap, which help explain the weak ferromagnetism measured in BaMo0.0625Sn0.9375O3−δ containing considerable oxygen vacancies. This study confirms that the contribution of orbital electron states and defects that were ignored in the conventional explanation should be considered to solve the elusive magnetism in diluted magnetic oxides and offers a guide to improve the magnetism.

Diluted magnetic semiconductors (DMSs) have drawn much attention due to their potential in spintronics and magnetoelectronics. Transparent conducting oxides, which are characterized by high carrier density and mobility, may provide a platform to realize room-temperature DMS oxides via the carrier-induced ferromagnetism. However, magnetic properties of DMS oxides are sensitive to their stoichiometry, and the magnetic performance of the same material synthesized by different groups or preparation methods may vary greatly. Therefore, it is important to clarify the relationship between the magnetic property and the lattice structure. Here, we investigate the magnetic property of Ru0.037Ba0.963SnO3 powders calcined in different atmospheres. It is demonstrated that for Ru0.037Ba0.963SnO3, the measured ferromagnetism is much weaker than the calculated one, and the ferromagnetism of the samples calcined in oxygen is stronger than that of the samples calcined in air. Electron spin resonance measurements show the existence of oxygen vacancies in Ru0.037Ba0.963SnO3 powders, and the first-principles calculations confirm that oxygen vacancies will suppress the ferromagnetism. This work offers a guide to synthesize diluted magnetic oxides with the desired magnetic property.

Interfacial charge and strain are two coupling effects in semiconductor/ferroelectric epitaxial heterostructures, which are pivotal for use in tailoring functionalities in devices. In this work, La0.04Ba0.96SnO3/0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 heterostructures with varying film thicknesses were prepared in order to understand both charge and strain's contributions to the electric-field induced resistance change. The relative resistance change to the lattice strain remains almost unchanged in those thicker films, while increases a little bit in those thinner films. This slight increase is related to the substrate constraint near the interface and follows Freund's strain relaxation model during the dynamic strain induced by the piezoelectric switch. A depletion layer model was also established to simulate the electroresistance variation from the interfacial charge effect. The depletion layer involves an equilibrium between capture and release of electrons by the acceptor-like defects near the interface region. The resistance change vs electric field evolves from a butterfly-like shape to a square-like when decreasing the film thickness, due to the joint effect of strain and interfacial polarization screening charge. This study provides an insight into understanding heteroepitaxial coupling and exploring their potential applications in oxide electronic devices.

Interfacial charge and strain distributions inside artificial perovskite ABO3 heterostructures often affect intriguing physical properties that are important to device performance. Normally, both charge and strain coexist across the interfaces, and their exact roles in determining the properties remain elusive. In the present work, La0.7Sr0.3MnO3 (LSMO) ultrathin films were grown on (001)-0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNPT) single-crystal substrates to discriminate between the effect of charge and strain on the transport and magnetoelectric properties. In heterostructures with thicker LSMO films, the strain effect dominates the resistance and the magnetic moment depends on the external electric field. With the decreasing LSMO thickness, the butterfly-like resistance–electric-field (R-E) and magnetization–electric-field (M-E) curves become loop-like, indicating that charge effects dominate strain effects in determining the electric field that controls the transport and magnetic properties. Furthermore, soft-x-ray absorption spectra of 32 and 4 nm LSMO/PMNPT samples at the Mn L edge under an applied electric field of ±6 kV/cm indicate that orbital reconstruction also plays an important role in interfacial magnetoelectric coupling.Interfacial charge and strain distributions inside artificial perovskite ABO3 heterostructures often affect intriguing physical properties that are important to device performance. Normally, both charge and strain coexist across the interfaces, and their exact roles in determining the properties remain elusive. In the present work, La0.7Sr0.3MnO3 (LSMO) ultrathin films were grown on (001)-0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNPT) single-crystal substrates to discriminate between the effect of charge and strain on the transport and magnetoelectric properties. In heterostructures with thicker LSMO films, the strain effect dominates the resistance and the magnetic moment depends on the external electric field. With the decreasing LSMO thickness, the butterfly-like resistance–electric-field (R-E) and magnetization–electric-field (M-E) curves become loop-like, indicating that charge effects dominate ...

Bismuth layer structured Aurivillius oxides have long been considered as traditional ferroelectric dielectrics, and they are feasible platforms incubating magnetic, ferroelectric, photonic, microwave, etc. properties for many important applications. It has been a longstanding challenge to achieve a certain charge carrier concentration and to narrow the bandgap in such transition metal complex oxides, yet realizing that semiconductivity is necessary for potential integration functions such as junctions in oxide optoelectronic devices. By inserting La1-xSrxMnO3 into the typical Bi4Ti3O12 ferroelectric host, we demonstrate semiconductivity and large bandgap tuning in Bi4Ti3O12-La1-xSrxMnO3 (0.3 ≤ x ≤ 0.7) solid solutions, in which a minimum resistivity value of ρ = 5021 Ω·cm and an optical bandgap value of Eg = 1.97 eV are obtained. Soft X-ray absorption spectra provide Mn and Ti charge valence states, indicating an almost constant Mn3.2+ state and an increase towards Ti4+ when raising the La/Sr ratio.

There is a long-standing challenge in the fabrication of layered oxide epitaxial films due to their thermodynamic phase-instability and the large stacking layer number. Recently, the demand for high-quality thin films is strongly pushed by their promising room-temperature multiferroic properties. Here, we find that by inserting a conducting and lattice matched LaNiO3 buffer layer, high quality m = 5 Bi6FeCoTi3O18 epitaxial films can be fabricated using the laser molecular beam epitaxy, in which the atomic-scale sharp interface between the film and the metallic buffer layer explains the enhanced quality. The magnetic and ferroelectric properties of the high quality Bi6FeCoTi3O18 films are studied. This study demonstrates that insertion of the conducting layer is a powerful method in achieving high quality layered oxide thin films, which opens the door to further understand the underline physics and to develop new devices.

Effect of a platinum bottom electrode on the SrBi5Fe1−xCoxTi4O18 layered oxide polycrystalline films was systematically studied. The doped cobalt ions react with the platinum to form a secondary phase of PtCoO2, which has a typical Delafossite structure with a weak antiferromagnetism and an exceptionally high in-plane electrical conductivity. Formation of PtCoO2 at the interface partially consumes the cobalt dopant and leads to the structural collapsing from 5 to 4 layers, which was confirmed by X-ray diffraction and high resolution transmission electron microscopy measurements. Considering the weak magnetic contribution from PtCoO2, the observed ferromagnetism should be intrinsic of the Aurivillius compounds. Ferroelectric properties were also indicated by the piezoresponse force microscopy. In this work, the platinum induced secondary phase at the interface was observed, which has a strong impact on Aurivillius structural configuration and thus the ferromagnetic and ferroelectric properties.